List of Reserved Words

Table of Contents

The following is a listing of predefined identifiers in PHP. None
of the identifiers listed here should be used as identifiers in any of
your scripts. These lists include keywords and predefined variable,
constant, and class names. These lists are neither exhaustive or
complete.

User Contributed Notes 4 notes

1. It would be nice for this list to differentiate those reserved words, which are language constructs used *with* parentheses (isset, unset, empty, eval, exit, die, ...) and those rather to be used *without* parentheses (all includes, echo, print, return, ...?)

This would really help define some common coding styles...

2. Do you write NULL, TRUE, FALSE or null, true, false? (I find CAPITAL letters better, however typing them can be annoying so I stick with using all lowercase letters, but what's the standard?)

Naming a PHP5 class "variant" (with a constructor called the same) and then making an instance of it using __autoload triggers an error which disappears as soon as the name is changed. This should mean that "variant" is also a reserved word.